1. Field of the Present Invention
The present invention relates to a packet compression system for compressing a packet, a packet restoration system for restoring a packet compressed by the packet compression system, a packet compression method for compressing a packet, and a packet restoration method for restoring a packet compressed by the packet compression method. Specifically, the present invention relates to a packet compression system for compressing a packet which will be transmitted by a wireless LAN (Local Area Network) system, a packet restoration system for restoring a packet compressed by the packet compression system, a packet compression method for compressing a packet which will be transmitted by a wireless LAN system, and a packet compression method for compressing a packet compressed by the packet compression method. In addition, the present invention relates to a packet compression system for compressing a packet which will be transmitted between gateways or between inter-LAN connecting devices, a packet restoration system for restoring a packet compressed by the packet compression system, a packet compression method for compressing a packet which will be transmitted between gateways or between inter-LAN connecting devices, and a packet restoration method for restoring a packet compressed by the packet compression system.
2. Description of the Related Art
Recently, access point devices connecting a wireless LAN and a global area network such as the Internet have begun spreading at home, businesses and the like. Among these access point devices, what deals with an IP (Internet Protocol) telephone appears. Further, while the IP telephone is a dedicated device in one case, an OS of a personal computer supports functions of the IP phone in another case. The IP telephone uses a protocol such as a VoIP (Voice-over Internet Protocol). The VoIP normally uses a UDP/IP (User Datagram Protocol/Internet Protocol) as third and fourth OSI (Open Systems Interconnection) layers except for a time when the IP telephone is controlled. In addition, the VoIP uses an H.323 protocol, a SIP (Session Initiation Protocol) or the like as fifth and following OSI layers. The H.323 protocol or the SIP uses an RTP (Real-Time Transport Protocol) or the like for communication control, voice communication, and moving picture communication.
Further, voice data communication is held using the RTP or the like on the UDP/IP between wired LAN zones including gateways, inter-LAN connecting devices, and the like.
A prior art document of the present application is as follows:
Japanese Patent Application Laid-Open Publication No. 2001-325166.
In the conventional wireless LAN, in order to hold a VoIP communication between a wireless terminal and an access point device, only up to six wireless terminals can hold the VoIP communication even if all the other kinds of communications are not held.
According to, for example, IEEE (Institute of Electrical and Electronics Engineers) 802.11b, a normalized maximum total communication frequency is eleven Mbps. However, when a VoIP communication is held, a total used frequency band is actually at most about one Mbps.
These situations occur not only in a case where a voice communication is held using the VoIP but also in a case where a voice communication is held using the other protocol, and a case where a moving picture communication is held using a predetermined protocol.
Furthermore, because transmitting a codec signal in an RTP packet or the like in real time is important, the codec signal is short. Accordingly, an IP packet that includes the RTP packet is short, with the result that an occupation ratio of headers in the IP packet increases and transmission efficiency is disadvantageously deteriorated.